Conventional solutions for path selection based on path quality monitoring, assessment, and prediction, such as the Converged Network Analyzer (CNA), address the problem of path selection for limited multi-homing topologies, and only control outbound traffic.
Other conventional solutions for such path selection, which use relays to address more complex network topologies, rely on overlay networks with tunneling techniques or with static provisioning of state in the relays, or on diverting the signaling path in order to effect a change in the media session path, or on a central application controlling the whole network.
Conventional solutions are described in multiple research publications in the area of path quality, including, for example, “Path Switching and Call Protection for Reliable IP Telephony”, B. Karacali1, M. Karol2, P. Krishnan1, J. Meloche1 and Y. Shen, Avaya Labs Report ALR-2006-038, “Measurement Techniques in On-Demand Overlays for Reliable Enterprise IP Telephony”, B. Karacali, M. Karol, P. Krishnan, K. Kumar, and J. Meloche, in Proceedings of the IEEE International Conference on Communications (ICC), 2006, “Improving VoIP Quality Through Path Switching”, S. Tao, K. Xu, A. Estepa, T. Fei, L. Gao, R. Guerin, J. Kurose, D. Towsley, and Z.-L. Zhang, in Proc. INFOCOM, 2005, which are incorporated herein by reference in their entirety.
Other conventional systems, which are no longer available, have attempted to provide dynamic re-routing of traffic to avoid congestion (http://www.venturetdf.com/new/doc/news-kagoor.htm).
Different conventional solutions describe methods of establishing connectivity through relays. For example, the future-standard Traversal Using Relays around NAT (TURN) allows a communications host to control the operation of a relay and to exchange packets with its peers using the relay. TURN is described in “Traversal Using Relays around NAT (TURN): Relay Extensions to Session Traversal Utilities for NAT (STUN)”, http://tools.ietf.org/html/draft-ietf-behave-turn-08, J. Rosenberg, Jun. 24, 2008, Internet Draft (work in progress, intended to become an IETF Standard), which is incorporated herein by reference in its entirety.
The TURN protocol can be used in isolation, or can be used as part of the future-standard Interactive Connectivity Establishment (ICE) mechanism that provides connectivity checks via multiple different paths, and that is designed to verify and establish connectivity through Network Address Translation (NAT). ICE will likely be an important standard in the area of Session Initiation Protocol (SIP) communications. ICE is described in “Interactive Connectivity Establishment (ICE): A Protocol for Network Address Translator (NAT) Traversal for Offer/Answer Protocols”, J. Rosenberg, Oct. 27, 2007, Internet Draft (work in progress, intended to become an IETF Standard), http://tools.ietf.org/html/draft-ietf-mmusic-ice-19, which is incorporated herein by reference in its entirety.
ICE provides for connectivity checks at the current moment in time (e.g., at session set-up time) in order to verify and establish connectivity. ICE can provide for measuring the current round trip time (i.e., the current delay) as an optimization on top of verifying connectivity. The ICE standard does not, however, provide robust assessments or measurements of path quality.